SVG importer ignores `clipPath` applied to a group

## Description

The SVG importer does not respect a `clipPath` applied to a group. Content that should be cropped to the clipping shape is imported without clipping. follow up of #4329

## Steps to reproduce

1. Open `clip-path.svg` in a browser or another SVG viewer. It appears as a blue circle because a circle clips a larger square.
2. Import the same file into Graphite.
3. Compare the imported result with the browser rendering.

## Expected behavior

Only the circular portion of the blue square is visible, matching the SVG rendering in a browser.

## Actual behavior

The clipping path is ignored and the full blue square is visible.

Start by reproducing the issue with clip-path.svg, comparing its browser rendering with the imported result in Graphite. Trace the SVG importer’s handling of clipPath applied to a group, and verify completion when the imported artwork shows only the circular portion of the blue square, matching the SVG rendering.

索引モデルが issue の本文から書いたものです。